Previously, it was known to manufacture rotating impeller fans from various metal materials. Such manufacturing processes often involved molding or machining fans from solid pieces of metal, or stamping individual components such as blades and backing plates from sheet metal and assembling the components together. As is apparent, such techniques require relatively expensive materials and are rather labor intensive.
Recently, it has been known to manufacture rotating impeller fans from a variety of plastic materials. Typically, such impeller fans are injection molded as a single unit. Known impeller fans typically comprise an annular base or backing plate with a plurality of blade members extending orthogonally upward therefrom and radiating outwardly from the center of the base. In typical prior art fans the transition where the blade meets the base comprises a solid blade member extending upwardly at a generally right angle to a continuous base plate.
The drawbacks to such known plastic impellets include their increased vulnerability to stress as a result of centrifugal forces and also to impact of foreign objects. Further, users have demanded that such plastic impellets be stronger, lighter and less expensive than prior designs. Unfortunately, the stronger and lighter weight materials are frequently much more expensive than the commonly used materials.
Thus, there is clearly a need in the art for an improved impeller design which will increase strength and reduce weight while using minimal amounts of conventional materials.